The assembly and transport of modern wind turbines condition the design because of their increase in size. While wind turbines continue growing in size and power generation capacity, their assembly has nevertheless become more complicated because of the need for even taller cranes, which are scarce on the market and costly to rent.
The current state of the art includes solutions for avoiding the use of cranes during wind turbine assembly. Most of these solutions involve assembly as mounting sections on top of the others, though the following examples involve mounting modules from below.
U.S. Publication No. 2009/0087311 presents a complex system for lifting a tower and subsequently its nacelle with a full rotor. Wind turbines erected in this manner usually stand at a height of between 40 and 90 meters, and are thus dwarfed by the 160 meter tower proposed herein. Additionally, the tower sections are covered by guide rails for engaging the structure actuators that lift the assembly. The lifting system is operated from the same nacelle, which is in turn secured by braces to support the moments that it undergoes.
Spanish Publication No. 2389345 discloses some clamps with radial movement to restrain the tower while incorporating the next sections. It also includes some vertical cylinders with perpendicular actuators for hold the wind turbine while it is being mounted. This solution falls short however in that the cylinders do not operate when the clamps engage and vice versa. While logically the wind turbine is not running while it is being erected, there are nevertheless loads derived from its own weight and the incidence of the air flow on the wind turbine. Such stresses create a bending moment, and the reactions should be, after all, vertical loads. Such vertical reactions should be sustained by the conceived system throughout the entire process. In Spanish Publication No. 2389345, when only the clamps engage, the sole vertical load would be the traction of the clamps against the tower. In order for this traction to suffice to balance the mentioned moment, the radial force would have to be so strong that it would create a dent in the tower. This is thus considered to be an insufficient solution to the problem that the present proposal solves.
The state of the art differs from the present disclosure mainly in that the design is specifically created to withstand the loads sustained by the lifting system during the assembly process, thus providing continuity in the load trajectory and a low load in the lower zone of the system. There is no need for redundant systems of clamps or cylinders (as contemplated in Spanish Publication No. 2389345), or reinforcement braces and rails for guiding the sections (as contemplated in U.S. Publication No. 2009/0087311).